Conventionally, for a liquid crystal display device employing a liquid crystal display panel, backlight illumination applying cold cathode fluorescent tubes is widely used. In recent years, backlight illumination is also being developed that uses light-emitting diodes (LED devices) in three colors of red light, green light, and blue light, so as to reproduce more vivid and more natural color tones.
Of these types of backlight illumination, one that is of large size and therefore requires high brightness uses a subjacent illuminating device, in which cathode fluorescent tubes or LED devices are arranged in a planar manner. On the other hand, one that is of relatively small size uses a lateral light-source, or commonly known as edge-light, planar illuminating device, in which the light from a light source is incident on a side surface (an incident surface) of a light-guiding plate and is emitted from one main surface (an emitting surface) of the light-guiding plate, so as to provide illumination.
It is considered that in the future, a liquid crystal display device will increasingly be demanded to be thinner and have a wider screen as in a wall-mounted television and the like. However, it is more difficult to make the subjacent illuminating device thinner than to make the edge-light illuminating device thinner, and on the other hand, it is impossible to secure sufficient brightness of the edge-light illuminating device if the device is used for a wider screen.
In response, an attempt to realize a thin wide-screen liquid crystal display device with the use of laser devices that have high brightness and are suitable for high power, as a light source of the edge-light illuminating device, is also coming under review.
The use of high power laser devices as a light source makes it possible to make the number of the components far smaller than the use of LED devices. On the other hand, in a simple structure where components are arranged on a side surface of a light-guiding plate, the number of the components is so small as to cause uneven brightness. Accordingly, the use of laser devices as a light source requires an optical system in which laser light is linearly spread so as to uniformly illuminate the side surface of the light-guiding plate.
A method of producing such linear illumination is disclosed in Patent Document 1, for example, which proposes a structure where LED devices are arranged on an edge surface of a rod-like light guide (a light-guiding rod) and thereby provide linear illumination. It is considered that this structure is also effective if the LED devices are replaced by laser devices.
In addition, in a liquid crystal display device, it is important not only to address a thin wide screen but also to address high brightness and low power consumption, and particularly, the reduction of the power of a backlight device, which constitutes the majority of the power consumption, is an important issue.
A method of such power reduction is disclosed in Patent Document 2, for example. Normally, light is emitted from a backlight while unpolarized, and therefore half the light is blocked by an incident-side polarizing plate of a liquid crystal display panel. However, the structure proposed in Patent Document 2 provides LED devices with polarization anisotropies so that backlight illumination is polarizable, and thereby improves the light utilization efficiency. Since laser devices are highly polarizable, it is considered that the use of polarization is also effective if laser devices are used.    Patent Document 1: Japanese Laid-Open Patent Publication No. 2000-11723    Patent Document 2: Japanese Laid-Open Patent Publication No. 2006-40639